All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Copolymerization of ethylene with α-olefins such as 1-hexene to generate linear low density polyethylene (LLDPE) is a widely used industrial process. The current industrial process involves the oligomerization of ethylene to generate α-olefins using an oligomerization catalyst, separation of 1-hexene or 1-octene from the oligomeric product mix, and subsequent copolymerization of the α-olefin with ethylene in a separate reactor using a different catalytic system to generate LLDPE.
Orthogonal tandem catalysis, where two independent catalysts operate together to perform consecutive transformations in a single reactor, would make this process more efficient and economical (FIG. 1). In order to devise an industrially relevant catalyst system we have developed a tandem version whereby both catalysts are co-supported on the same silica particles. By carrying out ethylene polymerizations with the catalyst in this form, the particle morphology of the polyethylene product is found to be highly uniform and free flowing without undesired “fines” (very small, dusty polyethylene components). Supported catalysts are widely used industrially in polyolefin synthesis due to ease of product isolation and to prevent clogging of industrial reactors from powdery, free moving polymer particles. While supported systems for a tandem route to LLDPE are known, in these cases the trimerization catalyst and the polymerization catalyst are on separate supports, which can cause numerous undesirable issues in an industrial process, such as catalyst segregation and inhomogeneity of the reaction mixture in the reactor over time. Therefore, there is a need for a tandem LLDPE catalyst, wherein the trimerization catalyst and the polymerization catalyst are both co-supported on the same silica particles.